Fixes #2941

Follow up #2902

* Fix regressions from #2683

Properly format spoiler text HTML, while keeping old logic for blankness intact
Process hashtags and mentions in spoiler text
Format spoiler text for Atom
Change "show more" toggle into a button instead of anchor
Fix style regression on dropdowns for detailed statuses

* Fix lint issue

* Convert spoiler text to plaintext in desktop notifications

* Very small fix/update NL strings

* Oops

* Add specs for valid challenge response from pubsub confirmation worker

* Refactor the pubsub confirmation worker

that caused user pages to break when showing toots with CWs

* Spec for feed insert worker when missing records

* more specs!

* Refactor feed insert worker

Vorbis is audio format of Open Source.
Can play audio in a free environment where you can not play mp3.

* Fix the pluralRuleFunction of the locale data.
* Added more descriptions about how to write it.

According to the release message:
> Fix for macOS and minor improvements

* services: scan spoiler_text for hashtags (#699)

* views: link hashtags from spoiler_texts

This covers linking hashtags from within the spoiler
text on the server-generated pages.

* services: fix string concat going into hashtag RE

Cleaner Ruby syntax, may handle immutable strings better

to all subscribers. IDN-normalize callback URLs for subscriptions on insert.

* Add spec for pubsubhubbub/subscribe

* Refactor pubsubhubbub/subscribe service

* Add coverage for pubsub unsubscribe service

* Refactor pubsub unsubscribe service

Compact Language Detector v3 (CLD3) is the successor of CLD2, which was
used in the previous implementation. CLD3 includes improvements since CLD2,
and supports newer compilers. On the other hand, it has additional
requirements and cld3-ruby, the FFI of CLD3 for Ruby, is still new and may
be still inmature.

Though CLD3 is named after CLD2, it is implemented with a neural network
model, different from the old implementation, which is based on a Naïve
Bayesian classifier.

CLD3 supports newer compilers, such as GCC 6. CLD2 is not compatible with
GCC 6 because it assigns negative values to varibales typed unsigned.
(see internal/cld_generated_cjk_uni_prop_80.cc) The support for GCC 6 and
newer compilers are essential today, when some server operating system
such as Ubuntu Server 16.10 has GCC 6 by default.

On the one hand, CLD3 requires C++11 support. Environments with old
compilers such as Ubuntu Server 14.04 needs to update the system or install
a newer compiler.

CLD3 needs protocol buffers as a new dependency. However,it is not
considered problematic because major server operating systems, CentOS and
Ubuntu Server provide them.

The FFI cld3-ruby was written by me (Akihiko Odaki) for use in Mastodon.
It is still new and may be inmature, but confirmed to pass existing tests.

ExtractTextWebpackPlugin extracts the content of loaded files, which means
it loads files loaded by require.context but not required after that.
However the former implementation is not aware of that.

require.context can have a RegExp to filter files to load. This change
gives a RegExp which matches with SCSSes with 'custom' prefix to
require.context to take advantage of the feature.

* add content-type in pubsubhubhub request header

* fix type

* Remove jquery-ujs

* fix for eslint

* Update Norwegian translations

* Updated no.json
* Updated activerecord.no.yml
* Updated no.yml
* Updated simple_form.no.yml

* i18n: fix Unicode character error in no.yml

* Javascript escaping code "\uD83D\uDC18" should be "\U0001f418" in
Ruby / yml

* i18n: remove unused keys in Norwegian translation

* Remove unused keys in no.yml and activerecord.no.yml
  by running: `bundle exec i18n-tasks remove-unused no`

* Add missing keys in activerecord.no.yml and no.yml by
  running: `bundle exec i18n-tasks add-missing no`

* i18n: escape the key 'no' in activerecord.no.yml

* Add specs for unsubscribe service

* Fix non existent methods in unsubscribe service

* Clean up status handling in subscribe service

* Coverage for api push controller

* Refactor the api/push controller

* Create reset_password_instructions.oc.html.erb

* Create reset_password_instructions.oc.text.erb

* Create password_change.oc.html.erb

* Create password_change.oc.text.erb

* Create confirmation_instructions.oc.html.erb

* Create confirmation_instructions.oc.text.erb